This invention relates to reducing the emission of electromagnetic energy from enclosures for electronic systems such as computers.
One of the challenges in the design of electronic system enclosures such as computer enclosures is to contain the emission of electromagnetic energy to an acceptable degree. Excessive emission of electromagnetic energy can result in electromagnetic interference (xe2x80x9cEMIxe2x80x9d) with other electronic systems. For this reason, laws and regulations exist to prohibit excessive EMI production by various kinds of devices; manufacturers must comply with such laws and regulations in the design of their products.
It is common to use sheet metal to form an enclosure because the sheet metal forms a Faraday cage, effectively containing EMI inside the enclosure. Unfortunately, any useful enclosure must include openings for mounting components, such as media drives and cables, that need to be accessible through or from the outside of the enclosure. Such openings in the sheet metal provide opportunities for EMI to escape, particularly when such openings are not populated with a component.
A need therefore exists for a technique that would enable components such as media drives and their cables to be mounted in a computer enclosure while at the same time effectively containing the escape of EMI from the enclosure.
In one aspect, the invention includes a conductive media drive housing having a removable rear EMI cover. When installed in an enclosure, the media drive housing and rear cover reduce the amount of EMI that can escape from the enclosure through the media drive bay opening. The media drive housing and rear cover are effective for reducing EMI whether or not a media drive is actually installed in the housing.
In another aspect, the invention includes the removable EMI cover itself. Made from a conductive material such as sheet metal, the EMI cover includes a surface for covering one end of the media drive housing. Flanges are disposed along the sides of the surface. A first one of the flanges is adapted to hingingly engage a first surface on the end of the media drive housing. A second one of the flanges is adapted to catchingly engage a second surface on the end of the media drive housing. Once the first flange is hingingly engaged with the housing, the cover may be rotated into a closed position in which the second flange catchingly engages the housing, thus securing the cover to the housing. To remove the cover from the housing, the catch is released and the cover is rotated into an open position from which it may be separated from the housing. Attachment of the cover to the housing is achieved without the use of fasteners, and removal of the cover may be accomplished by hand.
In another aspect, the hinging engagement between the cover and the housing may be accomplished with holes (or teeth) on the first flange that engage corresponding teeth (or holes) on the first surface on the end of the housing. The catching engagement between the cover and the housing may be accomplished with one or more detents (or holes) on the second flange that engage corresponding holes (or detents) on the second surface on the end of the housing. Protrusions disposed along the periphery of the cover may be provided to make conductive contact at corresponding points on the end of the housing, thus enhancing the EMI blocking characteristics of the cover.
In still another aspect, a cable management port may be provided without substantially impairing the EMI-blocking characteristics of the cover and housing: A flange of the cover may include a raised section through which a cable assembly may pass. The raised section may extend over a portion of the media drive housing when the cover is installed thereon, thereby defining a first channel. Enhanced EMI-blocking characteristics are achieved when the height and width of the channel so defined are not substantially greater than the height and width of the cable assembly. A second channel may be formed between an inside surface of the cover and a cable flange formed at the end of the housing. Further enhanced EMI-blocking characteristics are achieved when the first and second channels, end-to-end, form a combined channel having at least a 90-degree bend therein.